Combined specimen removal and vacuum distillation apparatus

ABSTRACT

A combined specimen removal and vacuum distillation apparatus for discontinuously checking liquid metal for purity, such as used as a heat carrier in nuclear reactor plants. The apparatus comprises a vessel of stainless steel forming a processing chamber and having wall-temperature control means and a removable top cover, means for positionally securing the cover on the vessel against excess pressure in the chamber, a plurality of removable specimen containers, holder devices mounted on the cover in suspended relation thereto for supporting the respective specimen containers, the holder means having respective heating means and respective temperature sensors, a lifting device having a tube vertically extending above the cover and tightly joined with the vessel chamber, a lifting mechanism disposed in the tube and connected to the cover for lifting the cover and the specimen containers, and a glove box and a specimen sluice interposed between the vessel and the tube of the lifting device.

United States n91 3,722.72 Jentges et al. 1 at. 27, 1973 541 COMBINEDSPECIMEN REMOVAL Primary ExaminerGerald A. Dost AND VACUUM DISTILLATIONAttorney-Curt M. Avery, Arthur E. Wilfond, Herbert PPARATUS L. Lernerand Daniel J. Tick [75] Inventors: Heribert Jeutges; ()skar Burz, both[57] ABSTRACT of 8520 Erlangen, Germany A combined specimen removal andvacuum distillal Assigneer siem'ens Akflengesenschafl, Berlin, tionapparatus for discontinuously checking liquid Munich, Germany metal forpurity, such as used as a heat carrier in [22] Filed: Oct. 30 1970nuclear reactor plants. The apparatus comprises a ves sel of stainlesssteel forming a processing chamber and [21] Appl. No.: 85,320 havingwall-temperature control means and a removable top cover, means forpositionally securing the cover on the vessel against excess pressure inthe [30] Foreign Application Pnomy Dam chamber, a plurality of removablespecimen con- Nov.7, 1969 Germany ..P 1955 988.7 tainers, holder devicesmounted on the cover in suspended relation thereto for supporting therespec- 521 U.S.Cl. ..266/34 R, 23/253 R, 356/36 five specimencontainers, the holder means having [51] Int. Cl ..C2lc 7/00 respectiveheating means and respective temperature 58 Field of Search ..266/34 R;23/253 R; 356/36, sensors, a lifting device having a tube vertically356/38; 73/61 LM tending above the cover and tightly joined with thevessel chamber, a lifting mechanism disposed in the [56] ReferencesCited tube and connected to the cover for lifting the cover and thespecimen containers, and a glove box and a UNITED STATES PATENTSspecimen sluice interposed between the vessel and the tube of thelifting device. 3,614,230 l0/l97l Crawford ..356/36 10 Claims, 2 DrawingFigures Patented March 27, 1973 3,722,872

2 Sheets-Sheet l Patented March 27, 1973 2 Sheets-Sheet 2 COMBINEDSPECIMEN REMOVAL AND VACUUM DISTILLATION APPARATUS Our invention relatesto a combined sampling and distilling apparatus applicable to adiscontinuous process for checking the purity of liquid metals, such asthose used as heat carriers in nuclear reactor plants.

In liquid-metal systems, especially liquid-metal circulation systems forthe conveyance of heat, chemical analysis of the liquid-metal melts todetect impurities, especially oxides, is of the highest importance sincethe rate of corrosion of structural materials depends essentially on thedegree of purity of the melt. Since reliablyoperating continuousapparatus for determining and recording such impurities do not exist,such determinations can be effected only by discontinuous processes ofchemical analysis.

The chemical analysis of liquid-metal samplings, particularly oxygendetermination, in any liquid-metal system is difficult since, on accountof the extremely minute impurity content, very slight traces of oxygensuffice to critically adulterate the samplings. In

nuclear-reactor primary-circulation systems using such liquid metals,radioactive'radiation is also present, allowing a chemical analysis of afew cubic centimeters of the melt only after the metal has been removed.

Distillation of the liquid metal is therefore a most promising processas a pre-stage for such chemical analyses, since with total vaporizationof metal no further metallic oxide can be generated through oxygen, andradioactive radiation due predominantly to the radioactivity of liquidmetal is substantially reduced. The residue of such samples can then beinvestigated for the types and amounts of impurities by means of'chemical analysis or flame-spectrometric methods.

Such'methods are well known, as illustrated by reports LA-3343 andLA-3879 of the Los Alamos Scientific Laboratory, published respectivelyin 1965 and 1968 by the University of California. The apparatus setforth therein are very complex and are equipped with' vitreousdistilling vessels. For safety reasons, they are therefore unsuitablefor the continuous operational investigation of liquid-metal samples,particularly if they become radioactive through irradiation in nuclearreactors. a

It is an object of the present invention to devise apparatus whichallows sampling as well as distillation without interference with theliquid-metal circulation system.

Another object of the present invention is to conserve the distillationresidue, if necessary, for subsequent investigation before it comes intocontact with oxygen.

removable top cover which prevents excess pressure when in position, andserves as a base for a number of movable sample tanks which includerespective holding devices provided with heating means and temperaturesensors. Furthermore, a lifting duct is arranged above the cover andtightly joined to the vessel chamber for lifting the cover together withthe sample tanks through a glove box and an outwardly dischargingsluice.

This apparatus contains no glass components and can be arranged in sucha manner that the distillation chamber itself together with theliquid-metal circulation systems which can also be contaminated withradioactivity are installed behind a suitable shield, such as cement,while the distillation residue can be taken away in a glove box situatedoutside the protected area, for further examination outside the chamber.To some extent the further investigation can take place inside the glovebox, but the samples can also be taken out through a sluice. Renewedoxygen contamination can be avoided by using a suitably pure protectivegas. Since a shield is provided between the glove box and thedistillation chamber itself, a further distillation cycle can commenceduring the examination of the residue. The present invention providesfor time saving which is a particular advantage when charging suchapparatus on the industrial scale, for instance, in sodium-coolednuclear reactor installations.

The above-mentioned and further objects, ad-

vantages and features of our invention will appear from FIG. 1 shows ourapparatus. in conjunction with a nuclear reactor circulation system 8for a liquid-metal coolant. System 8 comprises a reactor 81, a pump 82and a heat exchanger 83. The supply conduits to the distillationapparatus further include a a pump 84 and reflux tank 85. Thedistillation chamber 1 is connected with the liquid-metal circulationsystem through first and second outlet lines 16 and 17 and inlet line 3,with the reactor plant lying behind a shield 9 of concrete.

Beyond the shield, in a vacuum-tight extension of chamber 1 is a glovebox 6 and lift tube 7 wherein is mounted a windlass 71 having a rope 72,whereby a cover 13 of chamber 1 with the distillation residues suspendedtherefrom can be lifted by means of the rope through the concrete shieldinto the glove box for further treatment. As most of the radioactivityis in the liquid metal, the distillation residues contain only verylittle radioactivity and therefore are easily manipulated without fearof contamination. Beyond the concrete shield is a vacuum pump 5connected to chamber 1 through a liquid-metal condenser 51, and astorage .tank 181 for the protective gas.

As a feature of our invention, there are no plant components subject torepair inside the concrete shield, the

for replacement into the lift tube 7, which can be inspected afterclosing the supply conduit with a vacuumtight shut-off slide 64 onflanged joint 75, so that repair or replacement of such parts iscomparatively easy. The high-vacuum slide 64 can also be closed whencharging or discharging the system, thus providing a two-fold protectionagainst an unwanted supply of air, (for instance, the handling gloves 68becoming ripped).

According to FIG. 2, chamber 1 consists of a longitudinal steel vessel11, which is provided with an external heating means 14. Since changesof temperature of this vessel are required for accomplishing thedistillation process, heating means 14 is capable of cooling, working,for example, through a flow of liquid-metal having a temperature capableof being adjusted, whose circulation system is not shown in FIG. 2.Intensive cooling produces a short distillation time andcondensation ofthe highly radioactive sodium vapor inside the chamber.

Chamber 1 is closed by cover 13 having a sealing seat I 12 provided withits own heating or cooling means 15 which reenters into the chamberspace 1 to balance the thermal stress. The seat 12 has an upward tubularextension on which the cover 13 is maintained in a tightly sealedposition by wing screws 74. The screwing down of the cover isaccomplished inside glove box 6 and can be loosened by hand outside theconcrete shield.

Cover 13 also serves as a carrier for the sample tanks 23. For thispurpose it is provided with a holder frame 2 which is formed by threerigid supporting frames projecting downwardly, onto which the specimenholding devices 21 with heating means 22 for the sample tanks 23 rigidlyfastened. The cylindrical shape of sample tanks 23 combined with therounded transfer from the base to side wall and the cylindrical heatingconductor assemblies 22 promotes the heat input by short heat conductingpaths and intensive convection to the liquid level such that the shoftdistillation time is achieved without retardation of boiling.

The electrical connections for the heating devices 2 run through theholder frame 2 as do the connecting lines for temperature sensors 24mounted beneath the sample tanks 23 inside the holding devices 21. Theselines are carried upward above cover 13 in the form of a flexible,helical-wound cable 73, and drawn out (in a manner not shown indrawings) through vacuum-tight lead-in means from the lift tube 7 to theheight ofdrum or windlass 71 and connected to respective measuringdevices and/or sources of power (not shown).

The comparatively slight bulk of the holder or supporting frame 2facilitate excellent temperature control, which is of great importancefor setting the precise distillation temperature. Chamber 1 isfurthermore provided with an inlet 18 for the delivery of protective gasand is connected through supply tubes 31 witha liquid-metal supply 3merging with the reactor circulartion system. The tubes 31 terminate inthe interior of chamber 1 in the form ofjets and feed the liquid metalto be investigated to respective ones of the sample tanks 23. Chamber 1is further linked through outlet 16 to vacuum pump 5, the outlet line 16supplying liquidmetal into a reflux tank 85 when there is an overflow.

Emptying of chamber 1 is accomplished by discharge line or outlet 17which also leads into reflux tank 85. Closing of these inlet and outletlines 3, l7 and 16 is effected by freezing of gaskets 32, 171 and 161which are ganged in a conventional manner with a cooling apparatus (notshown). The freezing of the gaskets ensures a hermetic seal. Theinterior of chamber 1 is further provided with a rinsing means 33 whichis connected to the liquid-metal circulation system through line 34. Thesealing of cover 13 against tank 11 is achieved by the freezing-in ofthe liquid-metal condensate between the chamber and the sealing orclosing cone formed between cover 13 and seat 12. The sealing seat iscooled down by the cooling and/0r heating means 15 to 30 to 40C beneaththe freezing or solidifying' temperature of the liquid metal, so thatwith heat conduction, the sealing cone resting on the sealing seat is at20 to 30C above the freezing point. The liquid metal or the vaporthereof condenses on the bulging bottom of the sealing cone, runs downto the closure gap of the cone and freezes on the sealing seat itself.After the distillation process in chamber 1 terminates, the frozengasket is melted by warming heating coils 15. The condensate runs offoutwardly and is prevented from dripping into the crucibles 23.Normally, this apparatus is not subjected to any special pressure load,but if some unforeseen blockage of overflow 16 were to occur, a maximumexcess or overpressure of 16 atmospheres might occur which, as alreadymentioned, will be absorbed by the cover-fastening screws 74.

The operation of our apparatus as a whole will be described as followsfor a better understanding thereof.

First, chamber 1 is evacuated by means of pump 5 and thoroughly bakedunder the heating and/or cooling means 44. The heating and/or coolingfluid must be fluid and stable in the range from 0 to 650C andimpervious to radioactive radiation which might be emitted from thecontents of the chamber. Potassiumsodium melt is suitable, for instance.Subsequently, pu-

rified argon is poured into the chamber as the protective gas and theliquid metal, sodium, for example, for examination is squirted throughlines or tubes 31 from the reactor circulation system into the sampletanks 23. The overflowing metal through outlet line 17 forms a freezingplug in the gasket 171, so that the liquid-metal level in chamber 1rises up to the overflow level. The overflowing melt flows back into thereflux tank and from the reflux tank through pump 84 into the reactorcirculation system. When the liquid metal initially flows throughchamber 1, which is at a temperature of between 500 and 600C, residualgases especially 0xygen are chemically combined and washed away by theliquid-metal or vapor, and therefore no longer interfere with the sampleafter the metal commences being distilled. The tightsealing of the coverseating is, as mentioned above, secured by the metal condensate.

After about 4 hours, the inflow of liquid-metal is shut off and chamber1 empties through the lower discharge outlet line 17 through the meltingof the frozen plug 171. The liquid-metal supply line is shut off byfreezing of the metal at point 32.

The chamber cooling circulation flow is now commenced. In particular,the tubes of heating means 14 are supplied with coolant fluid and vacuumpump 5 is energized as soon as the wall temperatures drop to below C andthe crucible temperatures to about 350C, as sensed by means of thetemperature sensors 24. As soon as the required vacuum is obtained, the

crucible heater begins to operate, the liquid-metal present is distilledoff and again liquefied on the chamber walls and in condenser 51.

The end of the distillation is indicated by a sudden rise intemperature, so that after a short heating interval, preferable forreliable vaporization of any liquidmetal residues, the heating can beturned off. This completes the distillation process. Chamber 1 is purgedwith purified argon, and the condensate seal on cover 13 is melted.

Glove compartment 6 and lift tube 7 have been filled during the aboveprocesses with the protective gas, enabling cover 13 with thesample-tanks 23 dependent thereon to be raised manually or by anelectrically operated winch turning drum 71.

Inside the glove box, the sample tanks are taken off the holder devices21, given further treatment there and/or conveyed through sluice 62 tofurther testing equipment (not shown). A samplings carrier underprotective gas is required only if the samples are to be analyzed forelements present in the atmosphere and which react with the residuum.The crucible carrier is subsequently charged with fresh sampling tanksand again set in movement. The next filling and distillation process canimmediately start, since a renewed bakeout of wall partitions of chamber1 is no longer required. The walls of the vessel 11 can be cleansed inrotation through rinsing means 33, connected through an inlet pipe 34with a liquid-metal storage tank. Possible residues in the holdingdevices 21 can be rinsed clean without sample tanks.

With respect to the design of the sampling tanks, they can be made, forexample, of superpure nickel,

and it is preferable to round off the junction between the lateral wallsand the base in order to obviate any boiling of the liquid metal andformation of bubbles. The same end is served also by the direct heatingshown in FIG. 2 for the sampling tanks, on the surfaces of the shell,and their indirect heating in the fissure filled with liquid metalbetween the container base and holder device 21. This interstice isdimensioned in such manner that on distillation the sampling tank 23boils first and then the fissure. The vacuum thermocouple 24 senses thetemperature of the liquid metal in this fissure.

With a sampling tank capacity of about cm (appr. l 0. inch) the sodiumthroughput time will be about 4 hours as previously mentioned andthe-distillation time about one-half an hour, so that the examination ofthe distillation residue and likewise of the liquid metal circulating inthe circulation system can be effected during this period. It is thuspossible, with the plant, to survey the condition of the liquid-metalcirculation systems and other continuously-working metering equipmentand/or readjust the same.

This constitutes an extraordinary advantage of our apparatus, in thatthe sampling tanks filled with liquid metal do not have to betransported prior to distillation.- Other uses are also obvious, as wellas other constructional variations from the example here shown.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above method and aparatuswithout de arting from the scope of the inventhat all matter containedin the ion, it IS intende above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

We claim:

1. A combined specimen removal and vacuum distillation apparatus fordiscontinuously checking liquid metal for purity, such as used as a heatcarrier in nuclear reactor plants, comprising a vessel of stainlesssteel forming a processing chamber and having walltemperature controlmeans and a removable top cover, means for positionally securing saidcover on said vessel against excess pressure in said chamber; aplurality of removable specimen containers; holder devices mounted onsaid cover in suspended relation thereto for supporting said respectivespecimen containers, said holder means having respective heating meansand respective temperature sensors; a lifting device having a tubevertically extending above said cover and tightly joined with saidvessel chamber, a lifting mechanism disposed insaid tube and connectedto said cover for lifting said cover and said specimen containers; and aglove box and a specimen sluice interposed between said vessel and saidtube of said lifting device.

2. In apparatus according to claim 1, said specimen containers beingarranged above one another.

3. In apparatus according to claim 1, said vessel having a liquid-metalinlet, a first liquid-metal overflow outlet, a second liquid-metaloverflow outlet and a protective gas connection duct; a vacuum pumpconnected to said first overflow outlet, and a condenser interposedbetweensaid vacuum pump and said first overflow outlet.

4. Apparatus according to Claim 1, comprising a vacuum-tight shut-offslide between said vessel and said glove box for closing and openingsaid chamber relative to said glove box and sluice.

5. Apparatus according to claim 1, said specimen containers beingcrucibles, and said heating means for each of said. crucibles being anelectric resistance heater arranged'on said holder device for heatingthe crucible content through the crucible wall surface.

6. 'In apparatus according to claim 5, said crucibles having acylindrical cup shape and a rounded edge portion between the bottom andthe cylindrical wall of said cup shape.

7. In apparatus according to V claim 1 said lifting mechanism comprisingwindlass having a rope pull mounted in said tube near the top thereofand having a rope extending from said windlass to said cover.

8. In apparatus according to claim 7, said rope extending substantiallyalong the center axis of said tube.

9. Apparatus according to claim I, -comprising flexible helical windingsof cables for electrical connection to said heating means and to saidtemperature sensors, said helical cable windings extending upwardlythrough said tube in substantially coaxial relation thereto.

10. In apparatus according to claim 9, said vessel having vacuum tightlead-in means for said cables, said lead-in means being lo cated nearsaid windlass.

1. A combined specimen removal and vacuum distillation apparatus for discontinuously checking liquid metal for purity, such as used as a heat carrier in nuclear reactor plants, comprising a vessel of stainless steel forming a processing chamber and having wall-temperature control means and a removable top cover, means for positionally securing said cover on said vessel against excess pressure in said chamber; a plurality of removable specimen containers; holder devices mounted on said cover in suspended relation thereto for supporting said respective specimen containers, said holder means having respective heating means and respective temperature sensors; a lifting device having a tube vertically extending above said cover and tightly joined with said vessel chamber, a lifting mechanism disposed in said tube and connected to said cover for lifting said cover and said specimen containers; and a glove box and a specimen sluice interposed between said vessel and said tube of said lifting device.
 2. In apparatus according to claim 1, said specimen containers being arranged above one another.
 3. In apparatus according to claim 1, said vessel having a liquid-metal inlet, a first liquid-metal overflow outlet, a secoNd liquid-metal overflow outlet and a protective gas connection duct; a vacuum pump connected to said first overflow outlet, and a condenser interposed between said vacuum pump and said first overflow outlet.
 4. Apparatus according to Claim 1, comprising a vacuum-tight shut-off slide between said vessel and said glove box for closing and opening said chamber relative to said glove box and sluice.
 5. Apparatus according to claim 1, said specimen containers being crucibles, and said heating means for each of said crucibles being an electric resistance heater arranged on said holder device for heating the crucible content through the crucible wall surface.
 6. In apparatus according to claim 5, said crucibles having a cylindrical cup shape and a rounded edge portion between the bottom and the cylindrical wall of said cup shape.
 7. In apparatus according to claim 1, said lifting mechanism comprising windlass having a rope pull mounted in said tube near the top thereof and having a rope extending from said windlass to said cover.
 8. In apparatus according to claim 7, said rope extending substantially along the center axis of said tube.
 9. Apparatus according to claim 1, comprising flexible helical windings of cables for electrical connection to said heating means and to said temperature sensors, said helical cable windings extending upwardly through said tube in substantially coaxial relation thereto.
 10. In apparatus according to claim 9, said vessel having vacuum tight lead-in means for said cables, said lead-in means being located near said windlass. 